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Biomedical subjects

D F Mahoney

Publications and source records attributed to D F Mahoney.

At least 37 records · Page 2Linked to original sources
PubMed1984

Enzyme-linked immunosorbent assay for the detection of fermentation metabolites: aminoglycoside antibiotics.

A heterogeneous microplate enzyme immunoassay with a sensitivity of 10 pg/ml (1 pg/assay) toward gentamicin has been developed for the detection of aminoglycoside antibiotics in fermentation broths. Purified gentamicin antibody was coated onto the surface of the wells of microtiter plates and incubated with gentamicin-alkaline phosphatase conjugate. The amount of enzyme bound to the antibody was quantified by measuring the change in absorbance at 410 nm after the addition of the substrate, p-nitrophenylphosphate. Competitive assays performed by incubating the antibody and enzyme conjugate with various aminoglycosides showed that the antibody probe cross-reacted with all aminoglycosides tested, except neomycins B and C. No cross-reaction was detected with non-aminoglycoside antibiotics. Complex fermentation broths did not interfere with this assay. Cultures known to produce aminoglycosides were detected at levels well below the concentrations required for antimicrobial activity. This technique is useful in the identification, quantification and screening of fermentation metabolites.

Aminoglycosides↗
PubMed1983

The characterisation of an esterase derived from Babesia bovis and its use as a vaccine.

An esterase was isolated from a crude extract of Babesia bovis by affinity chromatography, using soy bean trypsin inhibitor as a ligand. In native form this enzyme had a molecular weight greater than 200 000, but on denaturing gels major bands were observed with molecular weights of 20 000, 10 000 and 7 000. Western transfer analysis revealed a major band with a molecular weight of 19 000-20 000. Both bovine and rabbit antisera avidly stained infected red cells, using indirect immunofluorescence. Weak parasite staining was also observed using this test. Two groups of five animals were vaccinated twice 4 weeks apart with esterase derived from 5 X 10(9) parasites as water-in-oil emulsions with Freund's complete adjuvant. Two control groups, each of five animals were also included. One group of vaccinates and a control group were challenged with virulent homologous B. bovis, whilst the other vaccinated and the remaining control group were challenged with virulent heterologous organisms. In the homologous groups two controls but no vaccinates died, whereas in the heterologous groups four animals in each group died. Significant differences in parasitaemia, temperature rise and total haemolytic complement were observed in the homologous vaccinated group compared to their controls but no differences were observed between heterologous groups.

Animals↗
PubMed1983

The enzymes of pyrimidine biosynthesis in Babesia bovis and Babesia bigemina.

All six enzymes of de novo pyrimidine biosynthesis leading to the formation of UMP have been demonstrated in whole homogenates from two bovine Babesia species, B. bovis and B. bigemina. The specific activities of the respective enzymes were of the same order of magnitude as observed for the related parasite, Plasmodium berghei. The results indicate that both these parasites have the potential of obtaining their pyrimidine requirements by de novo synthesis. Subcellular fractionation established that dihydroorotate dehydrogenase, the fourth enzyme of the pathway, was of a particulate nature. Mammalian respiratory chain inhibitors and ubiquinone analogues caused inhibition of the Babesia dihydroorotate dehydrogenase. As observed for other eukaryotic systems, the dehydrogenase appears to be linked to a respiratory chain via ubiquinone.

Animals↗
PubMed1983

Babesia bovis: isolation of a protective antigen by using monoclonal antibodies.

Three distinct monoclonal antibody-producing hybridomas have been produced against a partly purified protective fraction of Babesia bovis. All three stain the parasite or infected erythrocytes or both in precise and different manners when fluorescent-antibody techniques are used. The relevant antigens for each monoclonal antibody were isolated by immunoadsorption, their native molecular weights being 1.3 X 10(6), 180 X 10(3), and 44 X 10(3). Each antigen reacted in serological assays with homologous and heterologous bovine antisera to B. bovis. Susceptible splenectomized calves were immunized twice, 4 weeks apart, with the respective antigens and were challenged with virulent homologous organisms 2 weeks later. Strong protective immunity was induced by the antigen with a molecular weight of 44 X 10(3), but no significant protection was induced by either of the other two antigens.

Animals↗
PubMed1982

The irradiation of babesia bovis. II. The immunogenicity of irradiated blood parasites for intact cattle and splenectomised calves.

Intraerythrocytic forms of B. bovis were exposed to 350 Grays (Gy) gamma irradiation and were then injected intravenously into intact two and three year old Hereford steers. One of 15 steers died on initial infection and subsequently six steers were given a virulent heterologous challenge three weeks after recovery; all six animals were highly immune. The remaining eight animals were kept under quarantine conditions for 10 months and were then challenged with a different virulent heterologous strain of B. bovis. Seven of eight were highly immune, but one animal died. Subsequently a further 12 steers were injected intravenously with 1 X 10(8) irradiated organisms. All showed only mild transient clinical signs. After 12 months quarantine in a tick-free area these animals were then challenged with a virulent heterologous strain and all 12 were shown to be highly immune. Irradiation reduced the infective dose from 1 X 10(8) to 2.5 X 10(3) parasites. These parasites multiplied at the same rate, and achieved the same maximum parasitaemia as the parent non-irradiated strain, but the disease produced by them was not severe. A dose of 2.5 X 10(3) non-irradiated parasites was lethal to all of the four animals which received it. It was concluded that irradiation had produced a predominantly avirulent parasite population.

Animals↗
PubMed1981

Babesia bovis (Argentina): studies of plasma lipids and lipoproteins during acute infections in cattle.

Preliminary studies have demonstrated changes to the lipid metabolism of cattle acutely infected with Babesia bovis. Total lipid, total cholesterol, and phospholipids decreased significantly during infection. Associated with this was a decrease in concentration of serum lipoproteins and a loss of their electrophoretic heterogeneity. These changes are discussed in relation to the pathophysiological changes during infection.

Acute Disease↗
PubMed1981

The use of pathophysiological reactions to assess the efficacy of the immune response to Babesia bovis in cattle.

A group of five splenectomised calves was immunised with a soluble extract prepared from erythrocytes infected with Babesia bovis and then challenged by the intravenous inoculation of virulent B. bovis along with appropriate control animals. All controls died but four of the five immunised animals survived. All survivors showed significantly lower activation of the coagulation and kinin systems and did not develop the hypotensive shock syndrome characteristic of acute B. bovis infection. It was concluded that the concentrations of fibrinogen, kininogen, and bradykinin, and the production of soluble fibrin, cryofibrinogen, and high molecular weight fibrinogen complexes were useful criteria on which to assess the efficacy of the immune response.

Animals↗
PubMed1981

Bovine babesiosis: the immunization of cattle with fractions of erythrocytes infected with Babesia bovis (syn B. argentina).

Soluble antigen which protected susceptible cattle against challenge with Babesia bovis was extracted from B. bovis-infected erythrocytes by sonic disintegration and separation of the soluble from the insoluble matter by ultracentrifugation. The material was then fractionated by the precipitation of fibrinogen-like proteins. The precipitate contained the babesial antigens that were located on the stroma of the infected erythrocytes. Antigen originally located on the parasite remained in solution. Both fractions conferred protection on splenectomized calves against challenge with B. bovis. However, the fraction containing the parasite antigens appeared to have more potential for development as a killed vaccine because it was not heavily contaminated with antigenic material from bovine erythrocytes.

Animals↗
PubMed1981

Initial characterization of cryoprecipitates in cattle recovering from acute Babesia bovis (Argentina) infection.

The plasma of cattle recovering from severe babesia bovis infection contained cold precipitable protein which consisted of immune complexes formed in antibody excess. The major immunoglobulin in the complexes was IgM although IgG1 and IgG2 were also present at lower concentrations. In addition, fibrinogen, alpha 2 macroglobulin and C3 component of complement were detected. As the complexes were produced after parasiteamia fell below the detectable level and the inflammatory response to B. bovis was waning, the complexes did not appear to have much pathological significance.

Acute Disease↗
PubMed1981

Changes in conglutinin, immunoconglutinin, complement C3 and fibronectin concentrations in cattle acutely infected with Babesia bovis.

Further pathophysiological studies of the hypotensive shock syndrome associated with acute Babesia bovis infection in cattle have demonstrated changes in the plasma concentrations of conglutinin, complement C3, fibronectin and immunoconglutinin. Decreases in the first three components are presumably due to their contribution towards intravascular sludging of infected erythrocytes within the microvascular system during the acute phase of infection. In contrast, the increase in fibronectin and immunoconglutinin in the recovery phase suggests the involvement of these proteins in the reticulo-endothelial clearance of infected or damaged erythrocytes, immune complexes and cryofibrinogen.

Acute Disease↗
PubMed1981

Virulent and avirulent strains of Babesia bovis: The relationship between parasite protease content and pathophysiological effect on the strain.

A virulent strain of Babesia bovis ("L" strain) was rendered avirulent by irradiation with 35 krads with a gamma source. Another virulent strain of B. bovis ("C" strain) was made avirulent by rapid blood passage through 12 splenectomised calves. Both the parent virulent and their respective avirulent strains were injected into susceptible cattle. A nonfatal disease was observed in those intact cattle that had received avirulent parasites; however, a fatal disease was produced in those animals that had received virulent parasites and in splenectomised calves that had received avirulent parasites. Blood kinin levels rose and plasma kininogen levels fell significantly in those animals infected with both virulent strains. Nonsignificant changes occurred with these parameters in animals infected with avirulent parasites. Preparations of disrupted parasites were obtained from the four parasite populations. Both virulent strains contained high levels of protease. The avirulent forms contained insignificant amounts. As parasite doubling times and maximum parasitaemias were the same for all four parasite populations, we conclude that these enzymes are not obligatory for parasite multiplication in the vertebrate host. Their role in producing pathological changes in the host is discussed.

Animals↗
PubMed1981

The transmission of Babesia bovis in herds of European and Zebu x European cattle infested with the tick, Boophilus microplus.

Transmission of Babesia bovis by the tick Boophilus microplus was studied in 4 breeding herds of European and Zebu x European cattle under different levels of tick infestation. The observations consisted of weekly counts of female ticks on the cattle, monthly serological tests for antibodies to B. bovis, examination of tick larvae from the pasture to determine B. bovis infection rates and comparison of the suitability of paddocks for tick reproduction. The rate of transmission (inoculation rate) was estimated in terms of the daily probability of infection and consisted of the product of the mean daily tick infestation head-1 and the babesial infection rate in tick larvae. The theoretical value of the minimum inoculation rate required to produce stability of babesiosis is 0.01. This value was exceeded only in a herd of European cattle with minimal tick control and grazing on a pasture favourable for tick reproduction. Instability of babesiosis occurred in the other herds of European cattle after tick numbers had been reduced by pasture spelling and strategic dipping and after reduction in the babesial infection rate in ticks apparently caused by unfavourable environmental conditions. Over a period of years, the tick infection rates also declined as a consequence of the reduction in numbers of ticks. The Zebu x European cattle failed to generate inoculation rates greater than the minimum level, even though no tick control measures were applied. This was attributed to lower babesial infection rates in the ticks than those observed in a comparable herd of European cattle and to the high tick resistance of the Zebu crosses which maintained the tick populations at low levels. Both factors combined to produce a low inoculation rate.

Administration, Oral↗
PubMed1981

Procedure for assay of tobramycin in serum containing moxalactam.

Moxalactam was examined as a substrate for 11 beta-lactamases. Hydrolysis was shown only with the beta-lactamase from Bacillus cereus, a nonpathogenic bacterium. Tobramycin was assayed in tobramycin-moxalactam mixtures by using this beta-lactamase.

Anti-Bacterial Agents↗
PubMed1980

Changes in the haemolytic activity of serum complement during acute Babesia bovis infection in cattle.

The haemolytic activity of serum complement was measured in cattle during acute Babesia bovis infection. The level fell significantly on day 5 post infection (p.i.) and was not detectable by day 10 p.i. After clinical recovery between days 15 and 20 p.i. haemolytic activity was again detected in serum and gradually returned to the pre-infection level. The components of both classical and alternative pathways were involved in complement depletion and factors such as protease secretion by the parasites, antigen-antibody reactions, and the release of haemoglobin were implicated as causes of the decline. The absence of complement activity during the acute phase of the disease may interfere with immune mechanisms at a critical time for the host.

Animals↗
PubMed1980

Serum carboxypeptidase B levels during acute and mild Babesia bovis and acute Babesia bigemina infections of cattle.

Serum carboxypeptidase B (SCPB) levels were measured in splenectomised calves and in non-splenectomised cattle infected with three virulent and one avirulent strains of Babesia bovis, and in splenectomised calves infected with virulent Babesia bigemina parasites. SCPB levels commenced falling three days post-infection in animals infected with virulent B. bovis strains and fell significanttly terminally. In animals infected with the avirulent B. bovis strain, the SCPB levels were not significantly altered. Animals infected with B. bigemina had no significant changes in their SCPB levels. Fatal infections were uniformly observed in animals with virulent B. bovis, but only two of six animals infected with B. bigemina and none infected with avirulent B. bovis, died.

Acute Disease↗